Here's two quick points about sermons, based on some recent observations. I'll probably develop them more soon.
(1) Preach from the passage about what the passage says (and - the point needs reinforcing negatively - do not preach about what the passage does not say)!
The problem here is this: to preach on a topic not found in the passage undermines the notion of 'biblical preaching' which is that preaching connects the Bible to the congregation. Preaching on a topic or issue disconnected from the text is a legitimate form of preaching but it is not biblical preaching. And it should come with an honest statement, 'What I am about to preach on is important but it has no relationship to the passage(s) from the Bible which you have just heard!'
(2) By all means retell what the passage says, but go beyond retelling the passage (and any associated restating Christian doctrine) to apply the passage to the daily reality of the lives of your hearers. The problem here is that the Bible is connected with the Bible, with theology, with Christian knowledge, but it is not connected with the congregation.